An example of an object having multi-points to be welded includes a catalyst support for purifying exhaust gas. The catalyst support is composed of a base body formed by alternately laminating a flat sheet and a corrugated sheet and then winding them in a spiral shape, and an outer shell mounted around the outermost periphery of the base body for fixing the base body and enhancing the strength thereof. In such a catalyst support, the flat sheet needs to be welded to the corrugated sheet for preventing separation therefrom. However, there exist a number of contact points of the flat sheet to the corrugated sheet, that is, there exist a number of points to be welded corresponding to the contact points.
For joining the flat sheet to the corrugated sheet, there have been proposed techniques, for example, a brazing method disclosed in Japanese Patent Laid-open No. sho 61-199574 and a laser welding method disclosed in Japanese Patent Laid-open No. sho 63-185627.
Also, there has been proposed a method of joining the outermost periphery of the base body to the outer shell, for example, a caulking method disclosed in Japanese Patent Publication No. sho 57-55886.
However, the above brazing method disclosed in Japanese Patent Laid-open No. sho 61-199574 has a disadvantage that the metal made flat sheet or corrugated sheet is heat-affected in brazing to be deteriorated in its heat resistance.
Also, the above laser welding method disclosed in Japanese Patent Laid-open No. sho 63-185627 is a difficulty of perfectly joining all of the contact points of the flat sheet to the corrugated sheet. Accordingly, for perfect joining of all of the contact points, a laser beam needs to be scanned over the whole range of the end surface of the base body, which causes a problem of taking a long time.
Further, the above caulking method for joining the base body to the outer shell, disclosed in Japanese Patent Publication No. sho 61-199574, has a disadvantage that a joining process for the base body and outer shell must be separated from a base body forming process, thus increasing the time required for production.
Taking the above into consideration, an object of the present invention is to provide a multi-point welding method wherein multi-points to be welded are certainly welded for a short time. Another object of the present invention is to provide a method of producing a catalyst support for purifying exhaust gas wherein a flat sheet is certainly welded to a corrugated sheet for a short time thereby obtaining a catalyst support for a short time. A further object is to provide a catalyst support for purifying exhaust gas wherein a flat sheet is certainly welded to a corrugated sheet for a short time.